It is a fact that digital cameras have taken the place of most standard 35 mm. film cameras. The reason is that digital cameras today offer a high quality picture with 3, 4, 5 or even 10 megapixels in reasonable prices. This quality of picture is practically comparable to 35 mm. film pictures for digital cameras exceeding 3 megapixels.
There is a basic limitation however when using digital cameras. They are intended for “stills” picture (and sometimes also low resolution standard video filming) and therefore store the high resolution pictures in flash disks for later “off line” download to a P.C. computer. This download is usually done through a USB type cable (or over very short range wireless link like wireless USB extender).
Another form of download or “playback” is by using the “video out” or A/V analog output of the digital camera and connecting it to a video monitor or TV. This output however is limited from its nature to a vertical resolution of approximately 600 lines of pixels (the number of scanned lines in every video frame, or two interlaced video fields—odd and even) and a horizontal resolution of approx. 650 pixels (the number of black/white cycles possible within the normal 5 MHz bandwidth in timeframe of a single horizontal line—64 microseconds).64 uSec/100 nSec=640(100 nSec is the half cycle time of a 5 MHz signal).
The PC download gives the ultimate original resolution of the picture, but it is not suitable for real time download needed for long range wireless transmission. In order to extract the picture with its highest resolution (e.g. 3 megapixels or higher), and transmit it through a long range wireless link (in contrast with short range wireless LAN, Bluetooth etc . . . ), one needs to be able to communicate and handshake with a digital camera having a “slave” type USB interface, get the picture in a bitmap, JPEG or DVI format, and “pipeline” it through a very wideband wireless link that has a modem at both sides.
A compressed JPEG type picture of 3 megapixels (3 M×10 bit=30 Mb uncompressed), will have a typical size of 300 KB, or a minimum of 2.4 Mb of data, needing a very high quality wideband wireless link with modems+some pre and post processing to compensate for data loses and errors.
The difficult interfacing with the USB port of the camera (needing a PC type platform with operating system and software driver for the camera), and the high demands from the wireless link, make the long range USB type digital extraction extremely cumbersome, complicated and almost impossible in applications like mini UAVs (Unmanned Air Vehicles).
As explained before, the analog video output of the digital camera does give a real time output of the picture being taken or replayed, but it can not possibly display the full resolution of the stored picture in the camera in one single picture. You can either see the whole picture in low resolution, or a fraction of it in high resolution.
Another problem is that the most common video link today in UAVs is the analog video link capable of passing a real time standard video signal, 25 frames per second, with the above mentioned frequency limitations (5 MHz bandwidth, enough roughly to pass 650 pixels per line times 600 lines per picture, or roughly 0.3 megapixels per picture, 25 times per second). In wired closed circuit security observation systems (CCTV), the analog video link is still a major standard, with more or less the same specifications. It is therefore a matter of necessity to interface a low cost but high resolution digital camera to the existing video link of the UAV or a CCTV video link, while doing it with minimum of weight and cost, and getting the received picture on the ground (or monitor side for CCTV) with its original highest resolution with enough robustness to link noise, and in the best update rate.
The purpose of the invention is to show how to use, integrate and interface the digital camera in a UAV equipped with an analog video link, to achieve a near real time stream of megapixels stills pictures on a PC screen on the ground. The invention is useful in any remote sensing application needing high resolution pictures to be pipelined through an analog link (or even digital close to real time video links with composite video interface type).